Beyond Pricing: How to Find the Right Solar Module for Quality, Reliability and Performance

LONGi solar factory production line

Choosing the best module is not just about finding the lowest price; quality, reliability and performance of the product should be baked into any purchasing decisions. Just because a module passes the basic level of certification tests doesn’t mean it’s a high-quality, durable product. Modules need to be tested to the failure point, or at least through many more hundreds of testing cycles than what IEC or UL requires to get certified. But how do you tell which modules rate the highest for quality and reliability?

An excellent source of reliable, third-party information comes from the leading independent testing labs, such as PVEL (PV Evolution Labs), RETC (Renewable Energy Test Center), CSA and VDE. In PVEL’s case, each year the company publishes its PV Module Reliability Scorecard report, which offers crucial knowledge about long-term module reliability and performance data.

Based on PVEL’s rigorous Product Qualification Program (PQP), modules are put through a battery of lab and field tests. The testing goes beyond the model types of PV modules to assess bills of materials (BOM)—the cells, diodes, front glass, framing, lamination, backsheets and other components that comprise a solar module. This deep dive ensures that developers, EPCs and other buyers can procure the specific products that have been validated in PVEL’s testing.

The PVEL PQP tests include thermal cycling, damp heat, mechanical stress sequence, potential-induced degradation (PID), light-induced degradation (LID) + light and elevated temperature-induced degradation (LETID), and PAN performance, which strongly correlates to real-world performance when analyzing modeled versus measured results for this accelerated lifetime test regime.

For the 2022 report, PVEL awarded more than 100 module types from 25 manufacturers with its Top Performer status after testing. Of those companies, 12 manufacturers had one or more model types that were Top Performers in every reliability test—and six of those manufacturers, including LONGi, also earned Top Performer status in energy yield performance (PAN).

Module model types with less than 2% degradation for the highlighted PQP reliability tests received Top Performer status. For PAN performance, Top Performer status applies to those modules reaching a top quartile energy yield on the simulated PV sites presented in PVEL’s PAN reports.

These results are a tribute to the industry’s commitment to quality and reliability—although there is still work to be done. For example, while overall results for the thermal cycling tests were the best ever seen by PVEL, the lab also saw a troubling number of failures during testing, with nearly half of all participating manufacturers having a module that experienced at least one failure.

LONGI has submitted its modules for testing consideration to PVEL for six years, going back to the time the company launched its module business unit. For each of those six years, LONGi has been awarded Top Performer status. This year, the company submitted five modules from its production lines and was among those dozen companies that had at least one of those modules pass all six reliability tests—in LONGi’s case, its Hi-MO 4, 72-cell glass-glass bifacial module—as well as being one of the half-dozen companies that were Top Performers in energy yield performance (PAN).

As mentioned above, PVEL isn’t the only reputable independent testing lab LONGi works with. Our modules also go through rigorous testing at VDE, CSA and RETC to ensure our products’ bankability. In fact, the 2022 RETC PV Module Index (PVMI) has just been issued, and once again, LONGi has been recognized as a Top Performer for overall high achievement in manufacturing across the PVMI’s three categories of quality, performance and reliability.

In addition to LONGi’s strong belief in the need for third-party verification, the company has its own rigorous lifecycle quality system, which covers product design, new material selection and qualification, optimized manufacturing processes and after-sale service to ensure the reliability of its final products.

To hear more about PVEL’s 2022 Module Reliability Scorecard results and what makes a quality solar module, check out this episode of “The Pitch” featuring PVEL’s Tristan Erion-Lorico, LONGi’s CJ Fu and Solar Builder’s Chris Crowell:


By CJ Fu, LONGi Head of Product and System Solutions

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